The invention presented below concerns a method for the assembly of a wing according to the introduction to claim 1. Additionally, the invention involves a device for the assembly of a wing used in the implementation of the said method according to the introduction to the independent claim for the device.
A wing of an aircraft is normally constructed as a structure of spars and ribs, which is covered by a wing skin. The term stay is used below to include both the terms spars and ribs. The wing skin is generally fixed to the stays by means of screws. The stays underlying the wing skin have been formed in order to give the wing its profile and thus the final profile of the wing is formed when the wing skin is fixed to the underlying stay.
The stays supporting the wing skin are constructed of, for example, light metal such as aluminium, or, as is now common, composite. These stays consist of U-shaped sections with both upper and lower flanges against the upper and lower wing skin respectively. The flanges follow, as mentioned above, the surface profile of the wing in the stay""s vertical plane through the wing.
Since the wing skin is fastened by a large number of screws to the said flanges of the stays this assembly requires some type of nut or fixed thread in the dolly underlying the wing skin, that is in the flanges of the stays. With present-day technology this is performed by so called anchor nuts being fixed to the flanges of the stays on the side which faces away from the wing skin of the wing. Furthermore, the current technique is such that the anchor nuts have holed lugs which are suitably riveted to the inside of the flange. Supplying the frame, i.e. the stay, in this way with a thread in each position where a screw is to fix the wing skin to the frame makes fitting of the wing skin a simple procedure.
Assembly of the wing involves a number of steps. In the initial steps the frame is built using a jig, i.e. all of the wing""s stays are fixed together to produce the said frame. The skin of the wing is applied temporarily to the frame, after which, in the third step, the wing skin and frame are drilled jointly. This drilling means that holes for the wing skin""s mounting screws are drilled through the wing skin and the flanges of the stays in the frame during one and the same operation. In this way the exact positions are determined for the anchor nuts which in the subsequent assembly stage are to be fixed to the frame. In this stage of the assembly the wing skin has been removed, so that the operation of fixing the anchor nuts can be performed.
The work involving the fixing of the anchor nuts in position is very time-consuming when carried out manually. The nuts vary in type, so that holes for riveting of the lugs of the nuts have to be made and adjusted to the type of nut. Then the lugs of the nuts are riveted to the frame, that is to the flange of the stay. Drilling of the rivet holes must be done in the correct position so that the nut hole is aligned with the previously drilled screw hole in the frame. The holes for the rivets are of different diameters. The rivets vary in type according to the type of nut. All of this work requires a lot of time since thousands of anchor nuts must be fixed in position.
There are, on the market, solutions for the automatization of the drilling and riveting of anchor nuts. In large-scale production of aircraft wing units as described above there is one solution used whereby a clamp for handling tools has a range such that the tool at the end of both arms of the clamp can be extended in over the wing unit and reach every point of the same and is thereby capable of performing work operations on the top side and underside of the wing simultaneously. This process is automated, the operations being carried out according to a program. Such a solution, however, is expensive and requires large series for it to be profitable.
According to another method, a robot, which is able to move along the wing on a carriage, operates by looking for work positions using its robot hand, on which a automatic tool machine is mounted. The automatic tool machine grips the flange and holds the piece to be machined to the automatic tool machine. The automatic tool machine is constructed in such a way that, in a revolving fashion, it can select the tools in the correct order so as to carry out all the stages in the operation necessary for fixing an anchor nut in position. In this case the turret contains tools for making rivet holes, a device for transporting anchor nuts and placing them in the correct position, and a riveting tool for selecting the correct type of rivet and performing the riveting operation. An automatic tool machine of the said type designed for executing all steps in the operation is sophisticated and very expensive. Furthermore, having the tool holder secured in a turret means that the equipment is heavy and clumsy, thereby reducing the accessibility of the tool.
Another method which has been employed uses ordinary floor or carriage mounted six axle robots with a large range of movement which allows the robot to reach large areas of a wing. According to this method the robot, in accordance with a program, chooses a tool holder, supplies the tool holder with the correct tools, searches for the next work position, performs the first work operation, searches for a new work position, performs the first work operation again, and so on within a specified work area. When the first work operation is completed at all programmed positions the robot fetches and attaches to itself the next tool holder with the requisite tools, and performs all the elements of a second work operation. In trials using this method it has, however, proved difficult to achieve the exactness demanded in positioning the tool to the wing stays. Furthermore, neither does this type of robot with long arms and large manoeuvre area have the stability that is necessary, since there are large forces present between the mounted tool and the wing profile during certain work operations.
In order to find a solution to the above difficulties and, furthermore, to achieve an economically viable level of automatization for the assembly of a wing according to the description a new method and a new device for the assembly of a wing are presented here.
The invention constitutes a method and a device for the assembly of a wing of an aircraft. In the said assembly the wing skin is fixed to the wing frame using fasteners. The wing frame is built up of an number of stays with flanges to which the wing skin is secured. The fasteners are generally in the form of screws, although other types of fasteners are also possible. Fitting of the wing skin using fasteners involves various operations which have to be performed on the frame. Examples of such operations, in the case where the fasteners are composed of screws that are threaded into anchor nuts in the frame, are drilling of rivet holes, fitting of anchor nuts and riveting. Simultaneous drilling of the wing skin and frame to make screw holes is another example of an operation that can be performed according to the aspect of the invention.
According to an aspect of the invention in question a method for the assembly of a wing as specified in the independent method claims is presented.
According to a further aspect of the invention in question a device for the assembly of a wing as specified in the independent device claims is presented.
An advantage of using the method or the device according to the invention is that a robot with a relatively limited range of movement can be used. Thus, for example, a robot with an arm moved by ball screws can be used. This type of robot has a high degree of precision in locating work positions and can, in addition, withstand large tool forces, which produces stability when the various operations are being performed.
An additional advantage is that different tool holders are used for different operations. Such tool holders are relatively inexpensive and uncomplicated.